WO2015022986A1 - Mobile communication method and mobile communication system - Google Patents

Abstract

An objective of the present invention is to appropriately carry out reconfiguration of a U-plane bearer when a failure occurs in the U-plane bearer when User Equipment (UE) carries out Dual Connectivity. A mobile communication method according to the present invention comprises: a step of a wireless base station (SeNB) notifying a wireless base station (MeNB), when a failure is detected in a bearer which is configured between the wireless base station (SeNB) and the User Equipment (UE), to that effect and of the configuration information for the bearer; and a step of the wireless base station (MeNB) instructing the User Equipment (UE) to reconfigure the bearer between the wireless base station (MeNB) and the User Equipment (UE) on the basis of the configuration information.

Description

Mobile communication method and mobile communication system

The present invention relates to a mobile communication method and a mobile communication system.

In the LTE (Long Term Evolution) method, the mobile station UE is in a state of performing “Dual Connectivity”, that is, a macro cell under the radio base station MeNB (Macro eNB) and a small cell under the radio base station SeNB (Small eNB). The U-plane data is configured to be able to be transmitted and received between both the radio base station MeNB and the radio base station SeNB in a state where CA (Carrier Aggregation, carrier aggregation) is performed using .

In such a state, the mobility (handover) of the mobile station UE is configured to be controlled by the radio base station MeNB.

Moreover, when adding a small cell in the state in which the mobile station UE is communicating in the macro cell under the radio base station MeNB, between the radio base station SeNB managing the small cell and the mobile station UE , U-plane data bearer is configured.

However, in the conventional LTE scheme, when a failure occurs in the U-plane bearer due to some cause such as deterioration of communication quality in the small cell under the control of the radio base station SeNB in the above-described state, it is necessary for the U-plane data. There was a problem that it was not specified how to change the bearer settings.

Therefore, the present invention has been made in view of the above-described problems. When a failure occurs in the U-plane bearer in a state where the mobile station UE is performing “Dual Connectivity”, the U-plane bearer It is an object of the present invention to provide a mobile communication method and a mobile communication system that can appropriately perform resetting.

A first feature of the present invention is a mobile communication method in a state where a mobile station performs carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station, When the small cell radio base station detects a failure in the bearer set between the small cell radio base station and the mobile station, the small cell radio base station informs the macro cell radio base station to that effect and the bearer. The macro cell radio base station retransmits the bearer between the macro cell radio base station and the mobile station to the mobile station based on the setting information. And a step of instructing to set.

The second feature of the present invention is a mobile communication method in a state where a mobile station performs carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station, When a mobile station detects a failure in a bearer set up between the small cell radio base station and the mobile station, a reconfiguration request for the bearer is transmitted to the macro cell radio base station The step of acquiring the setting information about the bearer from the small cell radio base station based on the reconfiguration request, and the macro cell radio base station, Based on the setting information, the mobile station is instructed to reconfigure the bearer between the macro cell radio base station and the mobile station. And summarized in that a step of.

A third feature of the present invention is a mobile communication system in which a mobile station can perform carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station, wherein the carrier In a state where aggregation is performed, the macro cell radio base station has a first bearer MAC layer function, an RLC layer function, and a PDCP layer function, and the small cell radio base station 2 having a MAC layer function, an RLC layer function, and a PDCP layer function for two bearers, and when a failure is detected in the second bearer, the small cell radio base station The MAC layer function, the RLC layer function, and the PDCP layer function are deleted, and the wireless base for the macro cell is deleted. The station sets the MAC layer function, the RLC layer function, and the PDCP layer function for the second bearer, and the MAC layer function for the second bearer is commonly used for the MAC layer function for the second bearer. The gist is to set it to do.

A fourth feature of the present invention is a mobile communication system in which a mobile station can perform carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station, wherein the carrier In a state where aggregation is performed, the macro cell radio base station has a first bearer MAC layer function, an RLC layer function, and a PDCP layer function, and the small cell radio base station 2 having a MAC layer function, an RLC layer function, and a PDCP layer function for two bearers, and when a failure is detected in the second bearer, the small cell radio base station The MAC layer function, the RLC layer function, and the PDCP layer function are deleted, and the wireless base for the macro cell is deleted. In the station, the MAC layer function, the RLC layer function, and the PDCP layer function for the second bearer are set as independent entities for the MAC layer function, the RLC layer function, and the PDCP layer function for the first bearer. The gist.

A fifth feature of the present invention is a mobile communication system in which a mobile station can perform carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station, wherein the carrier In the state in which the aggregation is performed, the macro cell radio base station includes the RLC layer function and the PDCP layer function for the second bearer as well as the MAC layer function, the RLC layer function, and the PDCP layer function for the first bearer. The small cell radio base station has a MAC layer function, an RLC layer function, and a PDCP layer function for the second bearer, and when a failure in the second bearer is detected, In the small cell radio base station, the MAC layer function for the second bearer and the RLC layer The function and the PDCP layer function are deleted, and in the macro cell radio base station, the MAC layer function, the RLC layer function, and the PDCP layer function for the second bearer are set, and the MAC layer function for the second bearer is set. The gist is to set the MAC layer function for the first bearer to be used in common.

FIG. 1 is an overall configuration diagram of a mobile communication system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of the flow of U-plane data in the mobile communication system according to the embodiment of the present invention. FIG. 3 is a diagram illustrating an example of the flow of U-plane data in the mobile communication system according to the embodiment of the present invention. FIG. 4 is a sequence diagram showing an example of the operation of the mobile communication system according to the embodiment of the present invention. FIG. 5 is a sequence diagram showing an example of the operation of the mobile communication system according to the embodiment of the present invention. FIG. 6 is a diagram illustrating an example of a transition of the protocol stack of the radio base station MeNB / SeNB according to the embodiment of the present invention. FIG. 7 is a diagram illustrating an example of the transition of the protocol stack of the radio base station MeNB / SeNB according to the embodiment of the present invention. FIG. 8 is a diagram illustrating an example of the flow of U-plane data in the mobile communication system according to the first modification of the present invention. FIG. 9 is a diagram illustrating an example of transition of the protocol stack of the radio base station MeNB / SeNB according to the first modification of the present invention.

(Mobile communication system according to an embodiment of the present invention)
With reference to FIG. 1 thru | or FIG. 7, the mobile communication system which concerns on embodiment of this invention is demonstrated.

As shown in FIG. 1, the mobile communication system according to the present embodiment is an LTE mobile communication system, which includes a gateway device S-GW, a radio base station MeNB that manages a macro cell, and a radio that manages a small cell. A base station SeNB and a mobile station UE are provided.

Here, the radio base station MeNB may be referred to as a master radio base station (Master-eNB), and the radio base station SeNB may be referred to as a secondary radio base station (Secondary-eNB).

Also, the radio base station MeNB and the radio base station SeNB may be different physical nodes or the same physical node.

In the mobile communication system according to the present embodiment, the mobile station UE is configured to perform CA using a CC under the radio base station MeNB and a CC under the radio base station SeNB.

That is, in the mobile communication system according to the present embodiment, the mobile station UE is configured to be able to perform “Dual Connectivity” or “Inter-node UP aggregation”.

Further, in the mobile communication system according to the present embodiment, as shown in FIG. 2 and FIG. 3, when the mobile station UE performs “Dual Connectivity”, U-plane data on the same EPS bearer is The wireless base station MeNB and the wireless base station SeNB are configured to flow only to one of them.

Note that the U-plane data may be configured to flow from the gateway device S-GW to the radio base station SeNB as shown in FIG. 2, or as shown in FIG. It may be configured to flow to the base station SeNB.

Hereinafter, the operation of the mobile communication system according to the present embodiment will be described with reference to FIG. 4 and FIG.

First, an operation example 1 of the mobile communication system according to the present embodiment will be described with reference to FIG.

As illustrated in FIG. 4, in a state where the mobile station UE is performing “Dual Connectivity” between the radio base station MeNB and the radio base station SeNB, the radio base station SeNB performs the radio base station SeNB in step S1001. When a failure in the bearer set between the mobile station UE and the mobile station UE (for example, loss of synchronization in the uplink) is detected, in step S1002, the occurrence of the failure (Failure) is notified to the radio base station MeNB. Send “Connection Failure”.

For example, the radio base station SeNB may detect the occurrence of a failure in the above-described bearer (uplink) by monitoring PUCCH (Physical Uplink Control Channel) and SRS (Sounding Reference Signal).

In addition, the above-mentioned “Connection Failure” notifies “SeNB bearer configuration” indicating the setting information about the above-described bearer.

In step S1003, the radio base station MeNB transmits “RRCConnectionReconfiguration” to the mobile station UE in response to “Connection Failure”.

Here, the radio base station MeNB generates the above-described bearer reconfiguration information based on the “SeNB bearer configuration” notified by the “Connection Failure” and uses the “RRC Connection Reconfiguration” to the mobile station UE. Then, by notifying the reset information of the bearer, the radio base station MeNB and the mobile station UE are instructed to reset the bearer.

The mobile station UE performs bearer reconfiguration according to “RRCConnectionReconfiguration”, and transmits “RRCConnectionReconfigurationComplete” to the radio base station MeNB in step S1004.

Thereafter, in step S1005, the mobile station UE transmits / receives U-plane data to / from the radio base station MeNB using the reset bearer.

Secondly, an operation example 2 of the mobile communication system according to the present embodiment will be described with reference to FIG.

As shown in FIG. 5, the mobile station UE performs “Dual Connectivity” between the radio base station MeNB and the radio base station SeNB, and in step S2001, the mobile station UE performs a connection between the radio base station SeNB and the mobile station UE. When a failure in a bearer set between them (for example, RLF in the downlink, etc.) is detected, “RRC Connection Reestablishment Request” for requesting resetting of the bearer is transmitted to the radio base station MeNB in step S2002.

For example, the mobile station UE may detect the occurrence of a failure in the above-described bearer (downlink) by performing radio quality measurement or layer 2 measurement.

Here, as a failure detected by the mobile station UE, a failure in the physical layer (out of sync), “RACH problem”, “RLC problem”, or the like is assumed.

In step S2003, the radio base station MeNB transmits “UE Context Enquiry” requesting the radio base station SeNB to transmit the setting information about the bearer based on “RRCConnectionReestablishmentRequest”.

Here, “UE Context Enquiry” requests the radio base station SeNB to release the above-mentioned bearer.

In step S2004, the radio base station SeNB responds to the “UE Context Enquiry” with “UE Context Enquiry Response” to notify the radio base station MeNB of “SeNB bearer configuration” indicating the setting information about the bearer. Send.

In step S2005, the radio base station MeNB transmits “RRCConnectionReconfiguration” to the mobile station UE in response to “UE Context Enquiry Response”.

Here, the radio base station MeNB generates the above-described bearer reconfiguration information based on “SeNB bearer configuration” notified by “UE Context Enquiry Response”, and uses “RRCConnectionReconfiguration” to generate the mobile station UE. To the bearer reconfiguration information is instructed to reconfigure the bearer between the radio base station MeNB and the mobile station UE.

The mobile station UE performs bearer resetting according to “RRCConnectionReconfiguration”, and transmits “RRCConnectionReconfigurationComplete” to the radio base station MeNB in step S2006.

Thereafter, in step S2007, the mobile station UE transmits / receives U-plane data to / from the radio base station MeNB using the reset bearer.

Here, the protocol stacks of the radio base station MeNB and the radio base station SeNB before and after the bearer reconfiguration will be described with reference to FIG. 6 and FIG.

For example, as illustrated in FIG. 6A, in a state where the mobile station UE is performing “Dual Connectivity” between the radio base station MeNB and the radio base station SeNB, the radio base station MeNB includes the EPS bearer #. 1 has a MAC layer function # 1, an RLC layer function # 1, and a PDCP layer function # 1, and the radio base station SeNB has the MAC layer function # 2 and the RLC layer function # 2 for the EPS bearer # 2. And PDCP layer function # 2.

Thereafter, when a failure in the EPS bearer # 2 is detected, the radio base station SeNB deletes the MAC layer function # 2, the RLC layer function # 2, and the PDCP layer function # 2, and the radio base station MeNB The function # 2, the RLC layer function # 2, and the PDCP layer function # 2 may be configured.

Here, the MAC layer function # 2 may be set to use the existing MAC layer function # 1 in common (may have the same setting contents as the existing MAC layer function # 1).

As a result, as shown in FIG. 6 (b), the radio base station MeNB uses the EPS bearer # 2 together with the MAC layer function # 1, the RLC layer function # 1, and the PDCP layer function # 1 for the EPS bearer # 1. RLC layer function # 2 and PDCP layer function # 2 may be provided.

In such a case, the bearer reconfiguration information includes the identification information of the EPS bearer # 2, which has been set in the radio base station SeNB, the setting information of the PDCP layer function # 2, the setting information of the RLC layer function # 2, etc. It is included.

Alternatively, as shown in FIG. 7A, in a state where the mobile station UE is performing “Dual Connectivity” between the radio base station MeNB and the radio base station SeNB, the radio base station MeNB MAC layer function # 1, RLC layer function # 1, and PDCP layer function # 1, and the radio base station SeNB performs MAC layer function # 2 and RLC layer function # 2 for EPS bearer # 2. And a PDCP layer function # 2, and a failure in the EPS bearer # 2 is detected, the radio base station SeNB performs the MAC layer function # 2, the RLC layer function # 2, and the PDCP layer function # 2 And the MAC layer function # 2, RLC layer function # 2, and PDCP layer function # 2 are set in the radio base station MeNB. It may be configured to.

Here, MAC layer function # 2, RLC layer function # 2 and PDCP layer function # 2 are set as entities independent from MAC layer function # 1, RLC layer function # 1 and PDCP layer function # 1, respectively. Yes.

As a result, as shown in FIG. 7 (b), the radio base station MeNB uses the EPS bearer # 2 together with the MAC layer function # 1, the RLC layer function # 1, and the PDCP layer function # 1 for the EPS bearer # 1. The MAC layer function # 2, the RLC layer function # 2, and the PDCP layer function # 2 may be provided.

In this case, the bearer reconfiguration information described above includes the identification information of EPS bearer # 2 set in the radio base station SeNB, the setting information of PDCP layer function # 2, the setting information of RLC layer function # 2, , MAC layer function # 2 setting information and the like are included.

According to the mobile communication system according to the present embodiment, the mobile station UE performs “Dual Connectivity” between the radio base station MeNB and the radio base station SeNB using the EPS bearer # 1 and the EPS bearer # 2, respectively. Even if a failure is detected in the EPS bearer # 2 in the state of being in communication, the configuration of the EPS bearer can be appropriately changed and communication can be continued.

(Modification 1)
Hereinafter, the mobile communication system according to the first modification of the present invention will be described with reference to FIG. 8 and FIG.

In the mobile communication system according to the first modification, as illustrated in FIG. 8, when the mobile station UE performs “Dual Connectivity”, U-plane data (for example, EPS bearer # 2) on the same EPS bearer. The upper U-plane data) is configured to flow to both the radio base station MeNB and the radio base station SeNB.

In this case, as illustrated in FIG. 9A, in a state where the mobile station UE is performing “Dual Connectivity” between the radio base station MeNB and the radio base station SeNB, the radio base station MeNB A wireless base station comprising a RLC layer function # 1 and a PDCP layer function # 1 for EPS bearer # 1 together with a MAC layer function # 1, an RLC layer function # 1 and a PDCP layer function # 1 for # 1, The SeNB includes a MAC layer function # 2, an RLC layer function # 2, and a PDCP layer function # 2 for the EPS bearer # 2.

Thereafter, when a failure in the EPS bearer # 2 is detected, the radio base station SeNB deletes the MAC layer function # 2, the RLC layer function # 2, and the PDCP layer function # 2, and the radio base station MeNB Function # 2, RLC layer function # 2, and PDCP layer function # 2 are configured to be set.

Here, the MAC layer function # 2 may be set to use the existing MAC layer function # 1 in common (may have the same setting contents as the existing MAC layer function # 1).

As a result, as shown in FIG. 9 (b), the radio base station MeNB uses the EPS bearer # 2 together with the MAC layer function # 1, RLC layer function # 1, and PDCP layer function # 1 for the EPS bearer # 1. The RLC layer function # 2 and the PDCP layer function # 2 are provided.

According to the mobile communication system according to the first modification example, the mobile station UE performs “Dual Connectivity” between the radio base station MeNB and the radio base station SeNB using the EPS bearer # 1 and the EPS bearer # 2, respectively. In a state in which U-plane data on the same EPS bearer (for example, U-plane data on EPS bearer # 2) is configured to flow to both the radio base station MeNB and the radio base station SeNB Even when the failure is detected in the EPS bearer # 2, the configuration of the EPS bearer can be appropriately changed and communication can be continued.

The features of the present embodiment described above may be expressed as follows.

The first feature of the present embodiment is that the mobile station UE uses a macro cell under a radio base station MeNB (macro cell radio base station) and a small cell under a radio base station SeNB (small cell radio base station). In the mobile communication method in a state in which carrier aggregation is performed, when the radio base station SeNB detects a failure in a bearer set between the radio base station SeNB and the mobile station UE, A step of notifying the base station MeNB of the setting information about the bearer and the radio base station MeNB, based on the setting information, the radio base station MeNB and the mobile station UE And a step of instructing that the bearer be reset again.

A second feature of the present embodiment is a mobile communication method in a state where the mobile station UE performs CA using a macro cell under the radio base station MeNB and a small cell under the radio base station SeNB, When detecting a failure in the bearer set between the radio base station SeNB and the mobile station UE, the step of transmitting “RRCConnectionReestablishmentRequest (re-configuration request)” for the bearer to the radio base station MeNB The radio base station MeNB acquires setting information about the bearer from the radio base station SeNB based on the “RRCConnectionReestablishmentRequest”, and the radio base station MeNB sends the mobile station UE to the mobile station UE based on the setting information. And, and summarized in that a step of instructing to reset the bearer between the mobile station UE and the radio base station MeNB.

A third feature of the present embodiment is a mobile communication system in which the mobile station UE can perform CA using a macro cell under the radio base station MeNB and a small cell under the radio base station SeNB. In this state, the radio base station MeNB includes the MAC layer function # 1, RLC layer function # 1, and PDCP layer function # 1 for the EPS bearer # 1 (first bearer). The SeNB has a MAC layer function # 2, an RLC layer function # 2, and a PDCP layer function # 2 for the EPS bearer # 2 (second bearer), and when a failure in the EPS bearer # 2 is detected In the radio base station SeNB, the MAC layer function # 2, the RLC layer function # 2 and the PDCP layer function # 2 are deleted, and in the radio base station MeNB, M The C layer function # 2, the RLC layer function # 2, and the PDCP layer function # 2 are set, and the MAC layer function # 2 is set to use the existing MAC layer function # 1 in common. And

A fourth feature of the present embodiment is a mobile communication system configured such that the mobile station UE can perform CA using a macro cell under the radio base station MeNB and a small cell under the radio base station SeNB. When the CA is performed, the radio base station MeNB includes the MAC layer function # 1, the RLC layer function # 1, and the PDCP layer function # 1 for the EPS bearer # 1. The station SeNB has the MAC layer function # 2, the RLC layer function # 2, and the PDCP layer function # 2 for the EPS bearer # 2, and when a failure in the EPS bearer # 2 is detected, the radio base station In the SeNB, the MAC layer function # 2, the RLC layer function # 2, and the PDCP layer function # 2 are deleted, and the radio base station MeNB The function # 2 and RLC layer function # 2 and PDCP layer function # 2, and summarized in that to set as the MAC layer function # 1 and RLC layer function # 1 and PDCP layer function # 1 independent entity and.

A fifth feature of the present embodiment is a mobile communication system in which the mobile station UE can perform CA using a macro cell under the radio base station MeNB and a small cell under the radio base station SeNB. In this state, the radio base station MeNB has the MAC layer function # 1, the RLC layer function # 1, and the PDCP layer function # 1 for the EPS bearer # 1, and the RLC layer function # 2 and the PDCP for the EPS bearer # 2. The radio base station SeNB includes a MAC layer function # 2, an RLC layer function # 2, and a PDCP layer function # 2 for the EPS bearer # 2, and the EPS bearer #. 2 is detected, the radio base station SeNB detects the MAC layer function # 2, the RLC layer function # 2, and the PDCP layer function #. In the radio base station MeNB, the MAC layer function # 2, the RLC layer function # 2, and the PDCP layer function # 2 are set. For the MAC layer function # 2, the existing MAC layer function # 1 is set. The gist is to set it to be used in common.

The operations of the mobile station UE and the radio base station MeNB / SeNB described above may be implemented by hardware, may be implemented by a software module executed by a processor, or may be implemented by a combination of both. Also good.

The software modules include RAM (Random Access Memory), flash memory, ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electronically Erasable and Programmable, Removable ROM, Hard Disk, and Removable ROM). Alternatively, it may be provided in a storage medium of an arbitrary format such as a CD-ROM.

The storage medium is connected to the processor so that the processor can read and write information from and to the storage medium. Further, such a storage medium may be integrated in the processor. Such a storage medium and processor may be provided in the ASIC. Such an ASIC may be provided in the mobile station UE or the radio base station MeNB / SeNB. Further, the storage medium and the processor may be provided in the mobile station UE or the radio base station MeNB / SeNB as a discrete component.

As described above, the present invention has been described in detail using the above-described embodiments. However, it is obvious for those skilled in the art that the present invention is not limited to the embodiments described in the present specification. The present invention can be implemented as modifications and changes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention.

Note that the entire content of Japanese Patent Application No. 2013-169177 (filed on August 16, 2013) is incorporated herein by reference.

As described above, according to the present invention, when a failure occurs in the U-plane bearer in a state where the mobile station UE is performing “Dual Connectivity”, the U-plane bearer is appropriately reconfigured. It is possible to provide a mobile communication method and a mobile communication system.

S-GW ... Gateway device MeNB, SeNB ... Radio base station UE ... Mobile station

Claims (5)

1. A mobile communication method in a state where a mobile station performs carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station,
   When the small cell radio base station detects a failure in a bearer set between the small cell radio base station and the mobile station, the macro cell radio base station A step of notifying setting information about the bearer;
   The macro cell radio base station instructing the mobile station to reconfigure the bearer between the macro cell radio base station and the mobile station based on the setting information. A mobile communication method characterized by the above.
2. A mobile communication method in a state where a mobile station performs carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station,
   When the mobile station detects a failure in a bearer set between the small cell radio base station and the mobile station, the mobile station sends a reconfiguration request for the bearer to the macro cell radio base station. Sending, and
   The macro cell radio base station acquires setting information about the bearer from the small cell radio base station based on the reconfiguration request;
   The macro cell radio base station instructing the mobile station to reconfigure the bearer between the macro cell radio base station and the mobile station based on the setting information. A mobile communication method characterized by the above.
3. A mobile communication system in which a mobile station can perform carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station,
   In the state where the carrier aggregation is performed, the macro cell radio base station has a first bearer MAC layer function, an RLC layer function, and a PDCP layer function, and the small cell radio base station The second bearer has a MAC layer function, an RLC layer function, and a PDCP layer function,
   When a failure in the second bearer is detected, the MAC layer function, the RLC layer function, and the PDCP layer function for the second bearer are deleted in the small cell radio base station, and the macro cell radio base station The MAC layer function for the second bearer, the RLC layer function, and the PDCP layer function are set, and the MAC layer function for the first bearer is commonly used for the MAC layer function for the second bearer A mobile communication system, characterized by being set as follows.
4. A mobile communication system in which a mobile station can perform carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station,
   In the state where the carrier aggregation is performed, the macro cell radio base station has a first bearer MAC layer function, an RLC layer function, and a PDCP layer function, and the small cell radio base station The second bearer has a MAC layer function, an RLC layer function, and a PDCP layer function,
   When a failure in the second bearer is detected, the MAC layer function, the RLC layer function, and the PDCP layer function for the second bearer are deleted in the small cell radio base station, and the macro cell radio base station The MAC layer function, the RLC layer function, and the PDCP layer function for the second bearer are set as an entity independent of the MAC layer function, the RLC layer function, and the PDCP layer function for the first bearer. A mobile communication system.
5. A mobile communication system in which a mobile station can perform carrier aggregation using a macro cell under a macro cell radio base station and a small cell under a small cell radio base station,
   In the state where the carrier aggregation is performed, the macro cell radio base station has the RLC layer function and the PDCP layer function for the second bearer together with the MAC layer function, the RLC layer function, and the PDCP layer function for the first bearer. The small cell radio base station has a MAC layer function, an RLC layer function, and a PDCP layer function for the second bearer,
   When a failure in the second bearer is detected, the MAC layer function, the RLC layer function, and the PDCP layer function for the second bearer are deleted in the small cell radio base station, and the macro cell radio base station The MAC layer function for the second bearer, the RLC layer function, and the PDCP layer function are set, and the MAC layer function for the first bearer is commonly used for the MAC layer function for the second bearer A mobile communication system, characterized by being set as follows.

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